Pair of grippers for weaving looms without shuttle

ABSTRACT

A pair of grippers for shutterless looms, of the type wherein a first gripper (carrying) grasps the weft thread at one side of the loom and carries it to the center of the warp shed, while the second gripper (drawing) receives the weft thread at the center of the warp shed from the carrying gripper, and transports it to the opposite side of the loom, where it releases the same. The weft thread grasping and holding members are mounted on head parts of the grippers disposed on opposite sides of a sliding plane. Along said sliding plane said head parts move side by side, cooperating between them for grasping and releasing the weft thread.

This is a division of application Ser. No. 913,071, filed June 6, 1978,now U.S. Pat. No. 4,235,261.

BACKGROUND OF THE INVENTION

The present invention relates to important improvements in the wefttransport grippers for shuttleless looms, of the type wherein a firstgripper (carrying) grasps the weft thread at one side of the loom andcarries it to the centre of the warp shed, while the second gripper(drawing) receives the weft thread at the centre of the warp shed fromthe carrying gripper, and transports it to the opposite side of theloom, where it releases the same.

The pair of grippers according to the invention comprises grippers ofreduced weight and dimensions which cooperate with each other withoutpenetrating one into the other and which may move along a common plane,which may be differently oriented in respect of the plane of the loomreed.

SUMMARY OF THE INVENTION

The improved pair of weft transport grippers according to the inventionis essentially characterized in that, in both grippers, the weft threadgrasping and holding members are mounted on head parts of the grippersdisposed on opposite sides of a sliding plane, along which said headparts move side by side, cooperating between them for grasping andreleasing the weft thread. Said sliding plane may be parallel,perpendicular or differently inclined in respect of the plane of theloom reed.

The carrying gripper of the pair of grippers according to the inventionis characterized by a rear part, whose side close to the sliding planeprojects beyond said plane in respect of the head part of the gripper,so as to form a guide for the weft thread parallel to the plane itself,said head part comprising a pair of pegs for positioning the end of theweft thread, said pegs being arranged close to the free end of thethread grasping and holding means, on one side and on the other thereof,and in a position such as to cause the weft thread to be positionedbetween said guide and the first of said pegs only slightly inclined(about 25° at the most) in respect of the sliding plane.

Moreover, said carrying gripper mainly comprises a basic gripper body,the rear part of which is fixed to the gripper advancement strap andforms said guide for the weft thread, and the head part of which isequipped with said weft thread grasping and holding means, and a coveradapted to be applied on said basic body and comprising an opening forhousing said weft thread grasping and holding means, said pegsprojecting from said cover and fitting into said basic body orviceversa.

The drawing gripper of the same pair of grippers is also characterizedby the fact that the thread guard of its head part comprises a profiledappendix, extending parallel to the gripper body for covering the weftthread grasping and holding means.

The invention also comprises shuttleless weaving looms using theaforespecified grippers.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a front view of a loom part corresponding to the warp shed,showing a first type of a pair of weft thread transport grippersaccording to the invention, in a thread exchange position;

FIG. 2 is a section along the line II-II of FIG. 1;

FIG. 3 is a top view according to the arrow III of the arrangement ofFIG. 1;

FIG. 4 is a view similar to that of FIG. 1, but showing a modifiedembodiment of the pair of grippers according to the invention on theloom, in the position of weft thread exchange;

FIG. 5 is a top view according to the arrow V of the arrangement of FIG.4;

FIG. 6 is a top view of a third embodiment of the pair of grippersaccording to the invention in a condition which slightly procedes theweft thread exchange between the two grippers;

FIG. 7 is a front view of the body part of the carrying gripper, withthe cover removed;

FIG. 8 is a bottom plan view of FIG. 7;

FIG. 9 is a bottom plan view of the removed cover of the carryinggripper;

FIG. 10 is a front view of the removed cover of the carrying gripper;and

FIGS. 11 and 12 are a schematic side view and a fragmentary perspectiveview of the head part of the drawing gripper, illustrating the appendixfor protecting the thread guard of said gripper.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in the drawings, the pair of grippers according to theinvention comprises a carrying gripper 1 and a drawing gripper 2, inwhich the weft thread grasping and holding means 3 and 4 are mounted onhead parts 5 and 6 of the grippers themselves which are arranged on oneside and, respectively, on the other side of a plane α along which thegripper head parts 5 and 6 slide on each other in their working motion,cooperating between them with the mutually sliding parts of eachdisposed only on one side of that plane for exchanging the weft threadf.

In the arrangement of FIGS. 1 to 3, the plane α is perpendicular to theplane of the reed P, parallel to which are arranged the gripperadvancement straps or tapes 7 and 8, sliding in special guiding supports9, and the grippers themselves.

In the arrangement of FIGS. 4 and 5, the plane α and the grippers areagain arranged as in FIGS. 1 to 3, while their advancement straps arearranged along a plane parallel to the plane α and move along the same.

In the arrangement of FIG. 6, the plane α is parallel to the plane ofthe reed P and the grippers and straps are arranged, more traditionally,perpendicular to said reed plane and parallel to the top plane of thesley (as well as perpendicular to the plane α).

Although not shown, other arrangements of the grippers and straps couldbe provided, with the plane α lying inclined to different extents inrespect of the plane of the reed and of the plane of the sley.

The carrying gripper of the pair of grippers according to the invention(FIGS. 1 to 10) comprises a head part 5, in which are mounted the weftthread grapsing and holding members 3, consisting of a longitudinalelastic lamina 10, pressed by a leaf spring 11, which may for examplecorrespond to those of U.S. Pat. No. 3,580,291 and of a pair of pegs 12and 13, arranged close to the point of said elastic lamina, on one sideand on the other thereof. The head comprises moreover a rear part 14,whose side close to the sliding plane α projects beyond said plane.

The carrying head 5 is formed (FIGS. 7 to 10) by two elements of plasticmaterial associated with each other: a basic head body 16, the rear partof which 14' is fixed to the advancement strap 7, and the head part ofwhich is equipped with the elastic lamina 10, for grasping and holdingthe weft thread, and with the associated leaf spring 11; and a cover 17,applied to the basic body 16 and comprising an opening 18 for the lamina10 and related leaf spring 11. The rear part 14 of the cover 17 has itsside close to the sliding plane α projecting beyond said plane andbeyond the corresponding side of the rear part 14' of the underlyingbasic gripper body 16. On said cover side is formed a hollow guide 15for the weft thread, which is parallel to and spaced away from the planeα. The pegs 12 and 13 are carried by the cover 17, being fitted into theassembly in appropriate seats in the body 16 (of course, it could alsobe viceversa).

The removed cover 17 is separately shown in FIGS. 9 and 10, which latterfigure shows the cover in the same position as in FIG. 6.

The head part 5 of the carrying gripper 1 further comprises a top fin19, emerging perpendicular from the end of the body 16 which is notcovered by the cover 17, with the function of protecting the warp yarnsby preventing the weft thread grasping members from hitting the same. Itis moreover appropriate to create in the gripper body 16 a hardened zonecooperating with the elastic lamina 10, for example by applying intosaid body a hard metal element, or in some other way.

The drawing gripper 2 according to the invention has its head part 6(FIGS. 11 and 12) shifted sideways in respect of the rear part 20connected to the advancement strap 8. On the head part 6 of the gripperare arranged (FIGS. 11 and 12) weft thread grasping and holding means 4,of the type described in U.S. Pat. No. 4,040,454. The gripper 2 drawsthe weft thread from the gripper 1 when--as in FIGS. 1 to 6--these twomembers meet and their heads 5 and 6 come up side by side on a singleside. Such means comprise a fixed hook 21 and an oscillating lever 22,whose head wedges into the hook 21 so as to lock therein the weft threadunder the action of spring means 23 (FIGS. 1 to 6). According to theinvention, the head part 6 of gripper 2 is provided (FIGS. 11 and 12)with a thread guard 24 comprising a profiled appendix 25 extendingsubstantially parallel to the gripper 2 for covering the hook 21.

With the pair of grippers heretofore described and illustrated, the weftthread f will lie in the guide 15 of head part 5, in alignment with itsfeeding path and very slightly inclined (no more than 25°) in respect ofthis alignment (and thus in respect of the sliding plane α between theheads of the grippers) in the area between the guide 15 and the peg 12of the head 5 of the gripper 1, namely in the area in which the weftthread is grasped by the grasping elements 4 of gripper 2. Between thepeg 12 and the peg 13, the weft thread is instead arranged to extendbetween these pegs, being engaged by the elastic lamina 11.

The arrangement according to the invention introduces the use of lightand slender grippers (particularly remarkable in the case of thecarrying gripper, up to date always very bulky), which exchange the weftat the centre of the warp shed by simply coming close to each other withtheir head parts, on one side only, with evident progress and advantagecompared to the known technique of inserting the whole head of thedrawing gripper into an appropriate housing of the carrying gripper.

In fact, the surfaces of the two grippers coming into contact at themoment of thread exchange are reduced to a third, or even to a fourth,thereby preventing or highly reducing impacts, frictions, possiblejamming and failed grasping of the weft thread.

A further remarkable improvement and advantage is obtained, according tothe invention, thanks to the arrangement of the weft thread, which isslightly inclined in respect to its feeding alignment, in the grippingarea between the guide 15 and the peg 12 of the head 5 of the carryinggripper 1. Thanks to this arrangement, the weft thread is not subjected,at the moment of exchange, to the traditional front impact(substantially at 90° over a very short thread length) by the hook ofthe drawing gripper; on the contrary, the engagement takes place verysmoothly, progressively and over a very long thread length; this helpsto prevent, or at least to highly reduce cases of tears, abrasions andweakening of the weft thread, in general, which compromise the properoutcome of the thread exchange. This latter may be carried out with areduced braking of the thread and consequently with less breaks. Alsothe vibrations characteristic of the thread upon its exchange, arereduced, thereby improving even further the operation. On the otherhand, it should also be said that it is the actual aforedescribedarrangement of the weft thread in the grasping area which allows theconstruction of compact and light grippers, which are well balanced asto the distribution of the masses and which make it hence possible--asconfirmed by practical experience--to obtain weft insertion speeds whichare clearly higher than those obtained with the traditional systems,though keeping the mechanical stresses within reasonable limits.

The reduced dimensions and the specific shape of the grippers, asdescribed, allow one to eliminate in the carrying gripper according tothe invention the normal profile protecting the warp yarns, withremarkable advantages and, that is, extreme easiness of insertion, andconsequent reduction of the weft stresses and of the brakings requiredin order to overcome the inertia of the thread, as well as thefacilitated drawing out of the weft thread from the carrying gripperupon thread exchange, due to the absence of slippage and consequentfrictions which normally take place on the thread guard. The easiness ofthe weft disinsertion is also improved by the considerable simplicityand freedom of the weft thread guiding elements on the carrying gripper.

Finally, it should be noted that the appendix provided on the drawinggripper to protect the hook, favours the grasping of the weft by theappropriate members of such gripper, in that it opposes the possible"ballon" of the weft thread resulting from the deceleration of thegrippers movement upon thread exchange, thus allowing one to reduce thebraking power for the weft thread to be inserted.

I claim:
 1. In a pair of grippers for shuttleless weaving looms, of thetype wherein a first gripper grasps a weft thread at one end of a loomand carries it to the center of a warp shed, while a second gripperreceives the weft thread at the center of the warp shed from thecarrying gripper, and transports it to the opposite end of the loom,where it abandons the same, and weft thread grasping and holding membersmounted on head parts of the grippers and that cooperate between themfor exchanging the weft thread; the improvement in which portions ofsaid head parts of the grippers slide on each other over a portion ofthe path of the grippers immediately before and after weft threadexchange, the areas of contact between said portions of the respectivegrippers being disposed in only a single plane, said head portions ofthe grippers being disposed entirely on opposite sides of said plane fora length along each said head portion which is at least as great as thelength of said portion of said path.